Abstract
Motion sickness under experimental conditions cannot only be evoked through summation of vestibular Coriolis effects elicited during actual body rotation but also through optokinetic pseudo Coriolis effects evoked by head movements during an illusory body rotation. Hence, it is worthwhile to investigate the comparative effectiveness of some anti-motion-sickness drugs. The antihistamine, dimenhydrinate, and the belladonna-alkaloid, scopolamine, both reduce nausea and apparent tilt (separately scaled) after each head movement performed during pure vestibular, pure optokinetic and vestibular stimulation. The drugs diminish the occurrence of severe motion sickness as indicated by rating of symptoms and the number of subjects vomiting. Magnitude estimations of nausea and apparent tilt were found to be more reliable for evaluation of drug effectiveness than ratings. Vestibular nystagmns thresholds and subjective acceleration thresholds increase after drug administration, postrotational nystagmus is suppressed, and angular velocities of optokinetic saccades are lowered. Central sedative effects, about which subjects complained, were documented by psychological efficiency tests. On the basis of the results, one may hypothezise that the vestibular nuclei are a relay station also for provocation of optokinetics motion sickness and one of the possible sites of the pharmacological action in preventing optovestibular motion sickness.
